1. Field of the Invention
The present invention generally relates to magnetic storage apparatus, and more particularly, to a rotary head-type magnetic storage apparatus.
2. Description of the Prior Art
FIG. 1 is a block diagram showing an example of structure of a conventional magnetic storage apparatus. This magnetic storage apparatus is a rotary head-type digital audio tape recorder (referred to as R-DAT hereinafter) which is used as an auxiliary storage apparatus of an external computer 1. In the diagram, when data from the external computer 1 is to be written in a magnetic tape 14, it is applied to an interface 2 through a line l1. The data on the line l1 includes for example picture information, voice information, information to be processed in the external computer 1 and transmitted in information units (referred to as "frame" hereinafter) corresponding to two tracks of the magnetic tape 14 which will be described later. One frame contains, for example, 5120 bytes and the data is divided into the frames in the external computer 1 for output.
With the conventional apparatus in FIG. 1, one frame is divided into a plurality of areas as shown in FIG. 5. More specifically, for example, one frame comprises five data areas a to e and parity areas Pa to Pe individually corresponding to the data areas a to e. The above-mentioned data of 5120 bytes are divided into the data areas a to e each containing a data amount of 1024 bytes for being stored. Each of the parity areas Pa to Pe contains, for example, data of 128 bytes, which individually correspond to the data of the data areas a to e. The data in this parity areas Pa to Pe are added in the interface 2 for use as error correcting codes. In the R-DAT, parity addition is further performed in a signal processing circuit 7, where also the one frame composition shown in FIG. 5 ensures a further enhanced reliability of the R-DAT as an auxiliary storage apparatus.
The data is outputted to the signal processing circuit 7 through the interface 2 and a line l3 as well as to a random access memory 3 through the interface 2 and a line l2. The memory 3 is divided into eight memory areas M0 to M7 as shown in FIG. 3, each of which stores data of one frame.
In the memory 3, data of one frame from the interface 2 is first stored in the memory area M0. At this time, the respective data in the memory areas M0 to M6 is sequentially transmitted to the following right-hand memory areas M1 to M7 (cf. FIG.3). The data in the memory area M7 is generally deleted. For example, as shown in FIG. 3 (a), where data of frame numbers N+7 to N as will be described later are stored in the memory areas M0 to M7, respectively, when data of frame numbers N+8 and N+9 are sequentially entered, the memory 3 changes in the stored states shown in FIGS. 3 (b) and 3 (c). Input/output operation or the like at the interface 2 is performed according to a control signal from a control circuit 4 which is, for example, constituted of a microcomputer.
The parity addition in a general R-DATA is performed on the data which have been taken in the signal processing circuit 7 through the interface 2 and the line l3. The data with the added parity is outputted to an amplifier 8 through a line l4. A data signal which has been amplified by the amplifier 8 is applied to a writing head W1 through a line l5 and switched also for application to a writing head W2 through a line l6 to be written in the magnetic tape 14. The switching in the amplifier 8 is controlled by a signal from a synchronizing circuit 13 which has been synchronized with rotation of a rotating drum 9.
Such writing heads W1 and W2 and reading heads R1 and R2 as will be described later are fixed to the cylindrical rotating drum 9.
FIG. 2 is a perspective view of a structure of the rotating drum 9 and other parts associated therewith. The rotating drum 9 is driven by a motor 6 so as to rotate around its axis in the direction indicated by an arrow 20. At this time, a servo circuit 5 controls rotating speed of the motor 6 according to a control signal from the control circuit 4. Furthermore, the magnetic tape 14 is run for example by a capstan motor (not shown) in the direction indicated by an arrow 21. The magnetic tape 14 contacts a side surface of the rotating drum 9 at an angle of A1. This angle A1 is, for example, 90.degree..
The writing heads W1 and W2 are provided on a diameter line at side surfaces of the rotating drum 9. Similarly, the reading heads R1 and R2 are also provided on a diameter line at side surfaces of the rotating drum 9. The writing head W1 and the corresponding reading head R1 are provided with an angle A2 therebetween in the circumferential direction of the rotating drum 9 and slightly shifted with respect to each other in the axial direction. The angle A2 is, for example, 90.degree..
Such writing heads W1 and W2 scan on the magnetic tape 14 in a diagonal direction as shown in FIG. 4, resulting in tracks A and B. The above-mentioned frame numbers are recorded on parts of sub code areas 16a and 16b. The data having been written in the magnetic tape 14 are read out by the reading heads R1 and R2 which correspond to the writing heads W1 and W2, respectively. Signals from the reading heads R1 and R2 are applied to an amplifier 10 through lines l7 and l8, respectively. At this time, the reading heads R1 and R2 read out data on the tracks A and B, respectively, which have been formed by the corresponding writing heads W1 and W2.
The data signal which has been amplified by the amplifier 10 is outputted to a synchronizing circuit 11 through a line l9, where it is synchronized with a clock signal from a clock generating circuit 15. Meanwhile, the amplifier 10 switches, according to a synchronizing signal from the synchronizing circuit 13, the outputs from the reading heads R1 and R2 for output to the line l9. The output of the synchronizing circuit 11 is applied to a signal processing circuit 12 through a line l10, where error correction of the data is performed. This error correction is performed based on the parity which has been added in the signal processing circuit 7. The signal processing such as error correction at this stage is synchronized with that in the signal processing circuit 7 including the parity addition or the like, based on an output from the synchronizing circuit 13.
Data outputted from the signal processing circuit 12 is applied to the above-mentioned interface 2 through a line l12. Generally, the interface 2 stores the memory 3 with data through the line l2 and thereafter, reads out data from the memory 3 for output to the external computer 1.
As described above, in the conventional rotary head-type magnetic storage apparatus, the contact angle A1 of the magnetic tape 14 to the rotating drum 9 is 90.degree. and the attaching angle A2 between a writing head and the corresponding reading head is also 90.degree.. In this case, as shown in FIG. 6, reading may be done after writing is accomplished. With a smaller diameter of the rotating drum 9 (for example 30 mm or less), however, since the contact angle Al of the magnetic tape 14 exceeds 90.degree., it is required to perform writing and reading partially at the same time (see FIG. 7) in such a conventional head arrangement as shown in FIG. 1. As a result, there has arisen a problem of crosstalk being generated (transfer of a writing signal to the reading side).